No-vig odds calculator
Estimate the normalized probabilities behind a two-outcome market by removing the sportsbook's displayed overround.
Reviewed
Displayed overround: 4.76%. No-vig decimal odds: 2.00 / 2.00.
How proportional de-vigging works
First convert each price to raw implied probability. Then divide each probability by their sum. With two sides priced at -110, both convert to 52.38%. Their total is 104.76%; dividing each by 104.76% returns 50.00%.
In symbols, if the raw probabilities are pA and pB, the normalized estimates are pA / (pA + pB) and pB / (pA + pB).
Important limitation
This calculator uses proportional normalization. It is transparent and useful, but it assumes the margin is distributed proportionally between outcomes. Sportsbooks can shade one side, and long-shot markets can require more specialized methods. The result is an estimate of a no-vig market, not an objective true probability.
Use the result responsibly
Compare prices captured at the same time and under the same settlement rules. A stale price or a mismatched market can create a false difference larger than the vig itself. The guide to removing vig walks through the process and alternatives.